Treatment of molten metals



March 15, 1966 N. D. WEISS 3,240,589

TREATMENT OF MOLTEN METALS Filed May 16, 1963 INVENTOR NORMAN DAVID WEISS United States Patent 3,240,589 TREATMENT OF MOLTEN METALS Norman David Weiss, The Ards, Donridge, Warwickshire, England Filed May 16, 1963, Ser. No. 280,846 Claims priority, application Great Britain, May 29, 1962, 20,696/ 62 S Clmfms. (Cl. 7559) This invention relates to the treatment of molten metal and more particularly to the generation of gases Within molten metal. It is of particular interest in the degassing of molten metal by the generation of a flushing gas therein and will, therefore, be described With particular reference to that use.

It is well known to treat molten metal in order to remove from it hydrogen which is dissolved in the molten metal by generating in the metal a gas which will entrain or combine with such dissolved hydrogen. Thus, a carbon oxide may be generated in the molten metal by the decomposition of a carbonate, or chlorine may be generated in the molten metal by the decomposition of a fully chlorinated hydrocarbon, e.g. hexachlorethane.

Various methods have been described for carrying out this process. A common difliculty, however, is tohold the gas-generating unit below the surface of the molten metal, and preferably towards the bottom of the body of molten metal. Usually the unit is plunged below the surface of the molten metal by a plunger rod which holds it towards the bottom of the body of the molten metal.

It is an object of the present invention to provide a method whereby gas generation may be effected below the surface of the molten metal without the necessity for a plunger rod to hold the unit below the surface.

In the drawings, the single figure is a sectional elevational view of a degassing unit embodying the present invention.

According to the present invention a unit for generating gas, and suitable for use in the degassing of molten metal comprises a refractory container having a small neck opening and charged with a material which, at the temperature of the molten metal, will generate a gas. Preferably the vessel is shaped so that its centre of gravity is low in relation to its height.

It is found that when such a unit is immersed in molten metal the gases generated, in issuing through the narrow neck of the vessel, exert a reaction thrust on the vessel itself and drive it, by jet propulsion, towards the bottom of the body of molten metal, where it will stay until the gas-generation dies away. The thrust will then cease, and the vessel will return to the surface, and can so be removed from the molten metal.

The vessel is preferably formed of heavy refractory material and has a thick, and therefore heavy, base and a narrow neck opening. It is charged with gas-generating substance, e.g. a carbonate, for instance, dolomite, or a fully chlorinated hydrocarbon, e.g. hexachlorethane.

A typical form of vessel for use according to the inven tion is illustrated in the accompanying drawing wherein the vessel is made of heavy refractory material and has a narrow neck 1 and heavy base 2. It is charged with the gas generating substance 3 and the generated gases emerge through the opening 4 in the neck I.

If there is some degree of turbulence in the molten Patented Mar. 15, 1966 metal, caused for example by the gas-generation itself, it will deflect the vessel from its natural vertical position. Accordingly, the vessel will then be moved about, under the jet propulsion, but always below the surface of the metal. By having a heavy base to the vessel, the risk of the vessel tilting so that its base becomes uppermost is substantially eliminated.

I claim as my invention:

1. A method of introducing gas into molten metal which comprises introducing into the molten metal a unit comprising a refractory container having a small neck opening and charged with a material which generates gas at a predetermined elevated temperature, the center of gravity of said container being sufiiciently low in relation to its height so that said small neck opening remains at the upper end of said container when the container is immersed in the molten metal whereby the discharge of the generated gas through said opening submerges said container by jet action, said container being made of a material having a specific gravity lower than that of the molten metal so that the container is moved by the turbulence of the generated gases and returns to the surface of the molten metal when the gas generation ceases.

2. A method of introducing gas into molten metal which comprises introducing into the molten metal a unit comprising a refractory container having a narrow neck opening and charged with a material which generates gas at a predetermined elevated temperature, said container having a relatively thick and heavy base portion which provides said container with a center of gravity sufficiently low in relation to its height so that said container remains in a non-horizontal position with the narrow neck opening at the upper end of said container when the container is immersed in the molten metal whereby the discharge of the generated gas upwardly through said opening submerges said container by jet action, said container being made of a material having a specific gravity lower than that of the molten metal so that the container is readily moved by the turbulence of the generated gases and returns to the surface of the molten metal when the gas generation ceases.

3. A method of introducing gas into molten metal as defined in claim 1 in which the charged material is dolomite.

4. A method of introducing gas into molten metal as defined in claim 1 in which the charged material is a fully chlorinated hydrocarbon.

5. A method of introducing gas into molten metal as defined in claim 1 in which the charged material is hexachlorethane.

References Cited by the Examiner UNITED STATES PATENTS 2,134,905 11/1938 Bampfylde 59 2,395,458 2/1946 Cape 2759 2,770,860 11/1956 Webbere 7559 2,915,386 12/1959 Strauss 7558 FOREIGN PATENTS 503,583 6/ 1954 Canada.

DAVID L. RECK, Primary Examiner.

BENJAMIN HENKIN, Examiner. 

1. A METHOD OF INTRODUCING GAS INTO MOLTEN METAL WHICH COMPRISES INTRODUCING INTO THE MOLTEN METAL A UNIT COMPRISING A REFRACTORY CONTAINER HAVING A SMALL NECK OPENING AND CHARGED WITH A MATERIAL WHICH GENERATES GAS AT A PREDETERMINED ELEVATED TEMPERATURE, THE CENTER OF GRAVITY OF SAID CONTAINER BEING SUFFICIENTLY LOW IN RELATION TO ITS HEIGHT SO THAT SAID SMALL NECK OPENING REMAINS AT THE UPPER END OF SAID CONTAINER WHEN THE CONTAINER IS IMMERSED IN THE MOLTEN METAL WHEREBY THE DISCHARGE OF THE GENERATED GAS THROUGH SAID OPENING SUBMERGES SAID CONTAINER BY JET ACTION, SAID CONTAINER BEING MADE OF A MATERIAL HAVING A SPECIFIC GRAVITY LOWER THAN THAT OF THE MOLTEN METAL SO THAT THE CONTAINER IS MOVED BY THE TURBULENCE OF THE GENERATED GASES AND RETURNS TO THE SURFACE OF THE MOLTEN METAL WHEN THE GAS GENERATION CEASES. 